The present invention relates to document transport apparatus and in particular, but not exclusively, to document storage and retrieval apparatus employing a document storage drum.
Disadvantages can arise with such apparatus in that the speed of delivery of documents cannot be readily controlled. Commonly an undesired increase, or decrease, in the speed at which the documents are delivered by means of the transport apparatus cannot be readily prevented.
Such disadvantages arise particularly with document storage and retrieval devices employing a document storage drum in which at least one pair of belts are pinched together so as to hold a document therebetween and the pinched belts then wound upon the drum with the documents retained between the belts. The drum can be driven in either a clockwise or an anticlockwise direction so as to effect storage or delivery of the documents. The drum is driven at a constant speed and as the number of documents stored on the drum increases so does the diameter of the drum/belt arrangement. As the belts are unwound from the drum, the speed at which documents are retrieved from the drum decreases as the diameter of the drum/belt arrangement decreases. Such a variation in the speed of document delivery can prove problematic and limits the manner in which the document storage and retrieval device can offer a reliable, simple and user-friendly apparatus for the steady and controlled delivery of documents. Also, the manner in which such apparatus is currently operated requires that an appropriate tension is maintained in the belts and this places a further demand on the complexity of such apparatus which can lead to further problems arising in relation to the useful operation and maintenance of the apparatus.